Adenium Obesum Nutrient Requirements

Native to arid and semi-arid regions of Africa, Adenium obesum, commonly known as desert rose, is a succulent shrub or small tree that is often grown in containers and sometimes trained as bonsai. Although it evolved in poor soils, it does benefit from fertilizer. Desert rose can be grown outdoors in U.S. Department of Agriculture plant hardiness zones 10 through 12. When applying fertilizer, follow the label's instructions regarding the proper amount and recommended application for your desert rose.

Understanding Nitrogen Needs

Desert roses are slow growers. Grown outdoors, they grow fastest in their first three to five years, then slow down, growing as little as 6 feet tall in 15 years. To produce the maximum growth in early years, water them weekly when they are actively growing so they don’t dehydrate and fertilize with a high-nitrogen fertilizer. Fertilizer numbers show the ratio by weight of nitrogen, phosphorus and potassium. For example, a 20-10-10 would be a high nitrogen fertilizer, a 5-20-20 fertilizer would be a low nitrogen fertilizer. Unlike some species of Adenium, desert roses do not go dormant. Their growth rate does slow down in winter, and you should not fertilize them at that time.

Selecting Fertilizers

In an attempt to thicken their stems while stopping them from growing higher, a horticulturalist with the Arizona-Sonora Desert Museum experimented with a 2-10-10 low-nitrogen fertilizer on his mature desert roses. His plants did not thicken and flowered poorly; his well-fed plants flowered normally. Apply high nitrogen, balanced fertilizers in slow-release granules in early spring, in June and before November. Slow-release fertilizers that are coated with sulfur will release their nutrients in about eight weeks; if they are coated with polymer, they will release their nutrients in about 12 weeks. A balanced fertilizer contains nitrogen, phosphorus and potassium. You can also apply half-strength liquid fertilizer in irrigation water during their spring and summer growing season.

Fertilizing Large Plants in Pots

If you grow desert roses in a potting mix, use a 20-20-20 fertilizer with your irrigation water. A desert rose in an 18-inch-wide pot may grow several feet tall in three to five years or less. If you apply too much water or fertilizer in a potted desert rose that doesn’t get enough light and fresh air, it may suffer from weak, elongated growth, a condition known as etiolation.

Fertilizing Desert Rose Bonsai

Desert rose grown as bonsai does not need phosphorous to bloom. It does need high nitrogen to flower. During the growing season, feed desert rose bonsai monthly with a water-soluble, slow-release 13-13-13 fertilizer. Grown as bonsai, desert roses prefer a constant supply of low dose fertilizer rather than infrequent high doses.